Anionic polymerization of a lactam to give nylon has been known for many years.
In connection with nylons in general, the following developments of nylon are broadly germane.
In U.S. Pat. No. 3,018,273, a process for the in situ polymerization of caprolactam is described, wherein an organomagnesium compound is used as as an initiator, and an N,N diacyl compound is used as a promoter (or activator).
British Patent No. 1,067,153 describes a process for preparing nylon-block-copolymers by anionically polymerizing caprolactam in the presence of various initiators suitable for preparing nylon 6 polymers. Preparation of an isocyanate capped polypropylene glycol and a potassium based catalyst is described. A nylon block copolymer containing at least one polyether block is formed.
In U.S. Pat. Nos. 3,862,262, 4,031,164, 4,034,015 and 4,223,112 various aspects of the preparation of nylon block copolymers from caprolactam in the presence of an acyl lactam activator are described. U.S. Pat. No. 3,862,262 describes lactam-polyol-acylpolylactam block-terpolymers. U.S. Pat. No. 4,034,015 is directed to lactam-polyol-polyacyl-lactam or lactam-polyol-acyl-polylactam block terpolymers having at least about 5% ester end group termination. U.S. Pat. Nos. 4,031,164 and 4,223,112 describe lactam-polyolpolyacyl-lactam-block terpolymers having a specified ratio of the various components. More particularly, U.S. Pat. No. 4,031,164 discloses the use of 18 to 90% by weight of polyol blocks in the terpolymer.
U.S. Pat. No. Re. 30,371 describes preparing polyester-polyamide compounds by condensation of an alcohol and acyllactams in the presence of at least one of a Group IA, IIA, IIB, and IIIA metal or metal compound.
U.S. Pat. No. 3,925,325 describes a catalyzed process for the preparation of monomeric and/or polymeric compounds such as esters, polyesters, ester amides, and polyester-polyamides which result from the reaction of an imide and an alcohol in the presence of an organoaluminum, imide-alcohol condensation catalyst.
U.S. Pat. No. 3,965,075 describes using an amide on or organometal compound Group IVA, IB, IVB, VB, VIB, or VIII organometal compound for this condensation.
In European patent application No. 67693, laid open to public inspection on Dec. 22, 1982, acid halide materials and acyllactam functional materials are described as useful in the preparation of nylon block copolymers selected from the group consisting of those having the formula: ##STR1## Y is a C.sub.3 -C.sub.11 alkylene group; a is an integer equal to 1, 2 or 3;
b is an integer equal to or greater than 2; PA1 R is a di- or polyvalent group selected from hydrocarbon groups and hydrocarbon groups containing ether linkages; and PA1 Z is a segment of: PA1 b.sub.i is an integer.gtoreq.2, preferably and advantageously not greater than 4, PA1 Ci is an index relating to R, Ci is 0 or 1, wherein when Ci=0 then b.sub.i =2, PA1 n is the degree of polymerization for each nylon block, and preferably and advantageously 10&gt;n.ltoreq.1000, ##STR5## R has the following configuration ##STR6## wherein R' is a residue hydrocarbon radical derived from a polyol, such as PA1 a.sub.i has a value.gtoreq.o, and PA1 Y is: ##STR7## a hydrocarbon radical, an ether radical, and PA1 Z is the divalent hydrocarbon residue from a diisocyanate. PA1 caprolactam PA1 lactam catalyst PA1 polyol PA1 tin catalyst PA1 caprolactam adduct PA1 polyisocyanate PA1 caprolactam PA1 lactam catalyst PA1 caprolactam adduct PA1 isocyanate-terminated prepolymer
(1) a polyether having a minimum molecular weight of 2,000, PA2 (2) a polyester containing polyether segments having minimum molecular weights of about 2000, PA2 (3) a segment of a hydrocarbon or PA2 (4) a polysiloxane. PA2 a polyether polyol, PA2 a polybutadiene polyol, PA2 a polyester polyol containing one or more polyether blocks, or PA2 a grafted polyether polyol,
European patent application No. 67,695, laid open to public inspection on Dec. 22, 1982, describes a process for preparing a nylon block copolymer by reactively contacting a lactam monomer, a basic lactam polymerization catalyst and the acyllactam functional material described in European patent application No. 67,693.
European patent application No. 67,694, laid open for public inspection on Dec. 22, 1982, is directed to acid halide and acyllactam functional materials and to a process for the preparation of nylon block copolymers therewith. The acid halide or acyllactam functional materials are selected from the group defined by a complex formula.
The paper by Sibal et al, "Designing Nylon 6 Polymerization Systems for RIM", apparently presented in part as the 2nd International Conference on Reactive Polymer Processing, Pittsburgh Pa., in November 1982, describes preparing various initiators for anionically polymerizing lactams including a polymeric initiator. This initiator is prepared by reacting hexamethylene diisocyanate (HDI) with a polypropylene oxide diol, having an average molecular weight of 2000, by slow addition of the polyol (1 mole) to two moles of MDI. The resulting product was reacted with anhydrous lactam at 80.degree. C. No mechanical properties data are reported on the final product. Indeed, further work is said to be required to even begin exploring the processability and properties of the products. This paper also reports that reaction ratios and other process governing parameters are not known and further work is required.
U.S. Pat. No. 4,400,490 describes the anionic polymerization of a lactam with an epoxy-compound in the presence of a basic catalyst and a promoter. The epoxy compound can be the reaction product of a polymeric polyol and an epoxy compound.
U.S. Pat. No. 3,793,399 describes the use of a polyol, soluble in molten caprolactam, for improving the impact resistance of polycaprolactam. An organic nitrogen compound is used as a promoter in the polymerization.
The use of etherified polyols in the anionic polymerization of caprolactam is described in U.S. Pat. No. 3,770,689.
Polymerization of nylon in the automotive industry includes the use of "RIM" technology.
Reaction injection molding (RIM) is a one-shot injection method of liquid components usually by impingement into a mold where rapid polymerization occurs resulting in a molded plastic product. The pressures employed are much lower than in conventional injection molding processes. In a RIM process, the viscosity of the materials fed to a mold is about 50 cps to 10,000 cps, preferably about 1500 cps and the injection temperatures varying from room temperature for urethanes to about 150.degree. C. for lactams. Mold temperatures in a RIM process typically range from about 100.degree. to 220.degree. C. The mold pressures generally range from about 1 bar to 100 bar and more particularly the mold pressures range from about 1 bar to about 30 bar. At least one component in the RIM formulation consists of monomers and adducts thereof that are polymerized to a polymer in the mold.
For practical purposes, in a RIM-process the chemical reaction must take place rapidly in less than 2 minutes for smaller items. Presently, urethanes are commercially available for RIM processing although systems based on nylon and epoxy are said to be in development (Polymer Engineering and Science, Dec. 1982, Vol. 22, No. 17, pp. 1143-1152).
Injection molding is another process and is conducted at pressures of about 700 bar to 1400 bar in the mold cavity by melting a solid resin and conveying it into a mold maintained at room temperature while the temperature of the molten resin is about 150.degree. C. to 350.degree. C. At injection temperatures of about 150.degree. C. to 350.degree. C., the viscosity of the molten resin in an injection molding process is generally in the range of 50,000 cps to 1,000,000 cps and typically about 200,000 cps. In injection molding process, solidification of the resin occurs in about 10 seconds to 90 seconds, depending on the size of the molded product, following which, the molded product is removed from the mold. There is no chemical reaction taking place in an injection molding process when the resin is introduced into a mold.
RIM differs from injection molding in a number of important respects. The main distinction between injection molding and RIM resides in the fact that in RIM, a chemical reaction takes place in the mold to transform a monomer or adducts to a polymeric state.
Presently, nylon 6 block copolymers may be candidates for structure panels exposed to the surrounding environment. However, drawbacks weighing against the adaptability of nylon to RIM include the high moisture absorption rate of the product which could adversely affect dimensional stability between demolding, coating and/or application operations. Thus, mechaical properties such as impact strength--especially for the glass fiber filled products--water absorption, and flexural modulus must be improved. Otherwise, there will be obstacles to producing structural penels of nylon block copolymers on a commercial scale.
Another disadvantage of the RIM process for the preparation of nylon block copolymers is as follows. It is not possible to determine the molecular weight (or degree of polymerization) of the nylon blocks independently from the amount of rubber phase used and the molecular weight thereof.
In the anionic polymerization of a lactam, using a polymeric activator, only two degrees of freedom exist, viz. when the molecular weight of the initiator and the amount thereof, which usually determines the amount of rubber, have been fixed, the degree of polymerization is also fixed and vice versa.
It would be very advantageous if the amount of rubber phase incorporated in the system could be independent of the molecular weight of the nylon block in the nylon block copolymer.
The improvement of these properties, and other objects are achieved by the present invention.